There is a reason why more books have been written about Abraham Lincoln than almost any other person (save William Shakespeare and Jesus Christ).

Of course, there are the obvious explanations as to why Lincoln is so enticing. He was an inexperienced politician who spent less than two years in Washington, D.C. before arriving in the capital to guide the country through its greatest crisis. He was also the most eloquent writer our nation has ever elected to the highest office, and he crafted arguably the best prose in the English language. Finally, he was taken from this country before his time, and the grief that comes with frustrated hopes continues to move us to remember him today.

But the real reason Lincoln gets so much copy is not because of his achievements, his eloquence, or his assassination. Rather, Lincoln has what every historian desires in a subject—namely, complexity. The extant sources about his life are so diverse and so copious that Lincoln affords the historian the chance to recreate the man anew.

Consequently, the sheer number of eminent scholars who have already attempted this feat discourages many newcomers, and further causes the Lincoln fanatic to distrust the possibility that someone has unearthed a new part of a man as scrutinized as he. But that is precisely what Joshua Wolf Shenk does in his book Lincoln’s Melancholy:How Depression Challenged a President and Fueled His Greatness.

Shenk makes the fascinating case that Lincoln’s lifelong struggle with depression equipped him with the tools he needed to lead the nation through a bitter civil war that lasted four years and cost nearly 600,000 Americans their lives.

In doing so, Shenk proves three basic points. First, that Lincoln actually was severely depressed, and at points suicidal, throughout his life. Shenk marshals evidence from many sources. He shows that Lincoln may have been genetically predisposed to such a condition, given that his parents and many of his relatives also exhibited symptoms of depression.

He shows that Lincoln often confessed his depression to many of his closest friends. Lincoln once told a friend that he did not dare carry a knife for he was convinced he might slit his own wrists. He wrote poetry about suicide. He repeatedly made comments about his gloom, once saying, “I am now the most miserable man living.”

But the most convincing evidence does not necessarily come from Lincoln’s own confessions (which other historians have said are not uncommon in an age that valued sentimentality). Instead, it is the testimony of others. Shenk shows that everyone—from Lincoln’s closest friends to men and women who only met the man once—were overwhelmed by his sadness. Even more convincing are the attempts by his friends in 1838 and 1841 to prevent Lincoln from harming himself, like when they entered his apartment and removed all of the sharp objects, and conducted what psychologists would now characterize as a “suicide watch” for several days at a time.

Given the wealth of information, one would think this first task would not be so difficult. But Shenk is fighting against decades of scholarship that has insisted that Honest Abe’s depression is exaggerated or even non-existent. Shenk attributes this largely to a desire to focus on the great leader’s strengths, at the expense of facts that might complicate the mythic portrait so many want.

Once Shenk finishes the difficult task of proving what seems like an obvious statement of fact, he spends the majority of the book showing how Lincoln dealt with his depression and how profoundly Lincoln was affected by his struggle. We see how Lincoln used humor, mainly through his telling of stories to friends and strangers, to climb out of his spells. We learn of how Lincoln wrestled with religion, which he saw as both necessary to his life and an obstruction to his freedom to think as an individual.

For Shenk, Lincoln ultimately saw his world as a place of two truths: one, the basic fact of life is suffering, and two, humans are endowed with the remarkable ability to live with (not transcend) suffering through attaching themselves to a cause worthy of their sacrifice. Anyone who has read the Gettysburg Address, his speech at Cooper Union, or the Second Inaugural understands how critical this interpretation truly is.

What leads this book from being simply memorable to monumental is that it uses Lincoln’s depressive episodes as a prism through which the author reinterprets Lincoln. Shenk offers new insights into Lincoln’s marriage, his waging of the war, his two sons’ deaths, and, of course, his speeches.

Finally, this book is not simply worth reading for its contribution to the studies of the man. It is worthwhile because it deals with issues that we, as Americans, are loath to confront. Too often, politicians and pundits attack anyone who exhibits pessimism. Too often, we look for politicians who live on the sunnier side of life. And it is inconceivable that this country would ever elect a man who had convinced his hometown that he might be depressed, insane, and suicidal. Yet, according to Shenk, it was precisely these qualities that enabled Lincoln to be well prepared for the unprecedented rigors of his presidency.

More importantly, in a country in which nearly one out of every 10 people are on anti-depressants, and 800,000 citizens attempted suicide in 2005, what could be more important than a book that demonstrates how one of our greatest Presidents battled depression through his entire life and, in the process, led our nation through a conflict that ripped our country apart?

Surely one reason we read and need biographies is to see how ordinary people can do extraordinary things. In Lincoln’s Melancholy, by telling us “the story of a man who joined great pain and great power,” Joshua Wolf Shenk has given us a man whose apparent weakness became a source of uncanny strength not only for him, but also for the nation, then and now.